Energizing circuit for fluorescent lamps in series



May 8, 1951 c. A. PETERSON 2,552,111

ENERGIZING CIRCUIT FOR FLUORESCENT LAHPS IN SERIES- Filed May 9. 1950 IN VEN TOR. W4 Zmam BY. ,u aa K M4 Patented May 8, 1951 time! sures .rrsrtur oaFrI-cE ENERGIZING CIRCUIT FOR FLUORESCENT LAMPS IN SERIES Ca1 'l A. Peterson, Chicago, Ill. -Application-Ma-y'9, 1950, 'SerialNo.--1-60,'867

This. invention relates .to -autotransformerrflucrescent lamp energizing 'circuitsor apparatus ..for..a, plurality. of lamps in. series, more particu- .larly .to such a :circuit .or. apparatus. wherein: the thigh voltages which exist .in l ordinary circuits across ..terminals receiving the .lamps, when the lamps. areremoved therefrom and .while' a source of. energy. is connected: to "appropriate terminals; .are lacking, andit is .an. :obj eCtnOf the: invention to provide improved circuits .-.or apparatus :of

this character.

Fluorescent clamps, as .is well known in this art, requireal high.startinguvoltage and. ior reasons of economy thervindingsiofthe transformer utilized in.; the energizing. circuit. commonly are connected in.- autotransformer relationship since .insuch. casertheivoltage. of .the. transformertprimary. winding. in vaddition .to the voltage. of the ..transformertsecondary winding, is availablelfor lamp, starting. To limit the. currentthrough the lamps ,after starting, some form of u-ballast tapparatusis used, thevoltage across the lamp .or lampsaftergstarting being reduced thereby to a lower value. When a fluorescentllampvistremoved from its sockets or terminalsuand the source of power remains connected to. the trans- .fOIIIlBl5'IhB voltage needed. for starting reappears .a mss..th -..t rm. na s- ,The Underwriters Laboratories, for safety reasons, have fixed an upper liimt tothevoltage which may be present across the terminals of a -;fi uo13esc,ent lighting .flxture when .there is .no lamp therein. ,fIhis .limit restricts .sharply the number of fluorescent .lamps which maybe started in series andhas restrainedadoptionioi lamp circuitswherein-a plurality. of ,lamps are connected in series. The development of .sequence starting and, series pperating ,lamp circuitshas made; it possible to reduce thetotal starting voltage required much below thesum of the starting voltages of the lamps connected in serieshhlltitmaystill be .sufiicientlyhigh to be above the Underwriters Laboratories limit, -i.orv example, for long or highvoltage lamps. Accordingly, .it, i s a furtherdobject, of the invenv,tion to provide ;an improvedautotransformer fluorescent lamp energizingcircuit, for, series operation of two or more fluorescent ,lampswherein, when anyone .of;the lampsis absent or removed from its sockets or terminals, the volt- ..age thereacross is prevented from rising above a predetermined limit.

It is a further object of the invention to. pro- ,vide an improved autotransformer fluorescent 1amp,;ener izing circuit for series operation-of 2 twoor more-fluorescent lamps wherein, .when any -one -:=of theilampsuis absent or removed .from. its l socket .or terminals, the voltage across. the. terminals of .all the .lamps. is substantiallyiremoved.

-It.-is afurther object of the invention to provide an improved .autotransformer fluorescent alamp energizing [circuit fo series operation .of two. or I more fluorescent lamps wherein, :when ...each..one.of the lampsis absent or-removed 'from "the damp l its socket :or fixture, the .:circuit sup.- tplyingtvoltagettmthe primary winding ofrthe .transformer ...=is substantially interrupted.

It is a further object ofmthetinvention topro- .vide .an :..impr.o.ved 1. autotigansformer .afiuorescent .5 l lamp energizing circuit of the .-.character .indicatedwhichis lsimpletin .form, inexpensive to manufacture and.hasrelativelyriewparts.

It is .a' furtherobject-of the invention topmcvide ..an .improved Lautotransformer fluorescent .0 lamp energizing gcircuit of the character iindicated without the use of separatetswitches insulated. from; the fluorescent vlamp terminals.

In..carrying out the inventioni-innone iform, can. energizingcircuit for a -;pair 1 of fluorescent lamps. in series is tprovidedicomprising, a primary ewinding and-aisecondaryswindingl disposed: ona common .magnetic core and being .connectible effectively ,in an additive; .autotransformer relationin series withv the-pairsof. fluorescent. lamps,

3U the windings :having .1 sufiicient lvoltage i when =.so

connected to strike ..at. least 'one-ofrthe. lamps; a

.pair .of double. contact :.members each torrenggageably 1 receiving ..the ;.terminal of r a fluorescent --lamp 1 between the contacts .thereof, the double .contactstof .each tone-of .the. members defining-an effective-open circuitrexcept .when the terminal of a;fluorescent1;lamp is :therebetween, one contact. of, each one .of thenpairwofrmembers being connected to;-one;of theends, .respectively,of

40 ,the; primarycwinding, :the. other wontactof. :each

one of thepair. .ofmembers i being .connectible. to

.asource of energymandsa pair of.contacts. each ;for;:engagementmyathea terminal of .a5fluorescent lamp, each; of ,the:last.mentionednontacts being .connected to one of theends, respectively, of

, the secondaryinding.

;For a more complete. understanding ,of the in- ,vention,reference shouldtbeliad .to theaccom- :panyingdrawing in which..the -sole-ifigure is a diagrammatic view, partially. in .perspectiveofapparatusembodying the invention.

Referring :to :.the drawing, the invention is shown-embodied invan energizing circuit comprising-a ballast l l -to -which -energy may be supplied from a source sof' alternating voltage, a a pair of two contact circuit interrupting sockets I2 and I3 connected between the source S and the ballast, and a pair of single terminal sockets I4 and I5 also connected to the ballast, the sockets I2 and I4 being arranged to receive the terminals of one lamp I6, and the sockets I3 and I5 being arranged to receive the terminals of a second lamp ll. Lamps I6 and H are connected in series circuit with each other and with the windings of the ballast, as will be described subsequently in this specification.

The ballast i I, which commonly is a single unit, comprises a transformer having a primary or exciting winding I9 and a second winding I9, a consenser 2I in series with the secondary winding, and a series combination of a resistor 22 and a condenser 23 connected between windings I8 and I9. Windings I3 and I9 are wound on an iron core 24 and may be so wound and arranged relative to the core construction that the transformer has a high leakage reactance, as is well understood in this art. For example, the core may be made relatively long and narrow and the windings placed side by side, or a shorter core may be used and high reluctance shunts placed between the windings as is shown, for example, in Patent No.

2,346,621 to Joseph G. Sola entitled Alternating Current Supply System, and assigned to the same assignee as the present invention. The dotted line shown surrounding the ballast II may represent a case, for example, out of which extend the leads 25, 26, 21 and 28 to which the remaining apparatus is connected.

In one form of apparatus embodying the invention, the condenser 2| may combine with the leakage reactance of the transformer to form a series resonant circuit when the lamps are lit, as is described in the aforementioned patent of Joseph G. Sola. Other means for controlling the lamp current after the lamps strike may, of course, be used.

The windings I8 and I9 may have an appropriate number of turns, and the core 24 ma be of a size determined by standards well known in the art. The ratio of turns of winding I9 to I6 is such that a sufficient voltage is developed across the secondary winding I9 which, when added to the voltage of winding I8 (the supply voltage of proper magnitude and frequency), a sufficient voltage is obtained for starting the lamps in sequence and operating them in series. The windings I8 and I9 connected to the lamps I6 and IT, as shown, are in autotransformer relationship and are connected in additive polarity since the voltages of the two windings add to each other. The series combination of resistor 22 and condenser 23' connected across the conductors 26' and 21 form a starting circuit in shunt with lamp I'I whereby the lamp I6 may be struck first followed by striking of the lamp I'I. While the starting circuit shown is a preferred form thereof, either the resistor or the condenser may be omitted provided the value of the remaining member is changed slightly to compensate therefor.

The socket I2 includes a pair of contacts 29 and 3I held in an insulating support 32 which, for example, may be formed of Bakelite. The forward portions of contacts 29 and 3| are spaced apart from each other to form an open circuit and are spaced sufficiently close together so as to spread apart for receiving the single prong terminal 33 of lamp I6, and the rearward portion of contacts 29 and 3I are adapted to receive terminal screws 34 and 35 for attaching conductors to the contacts. The rearward portions of the contacts and the terminal screws are received in appropriately formed openings in the insulating support 32 and a fiber or other insulating washer 39 may be disposed over the terminal screws for insulating purposes. The socket I3 is substantially identical to socket I2 and includes a pair of spaced apart contacts 36 and 31 held in an insulating support 38. The forward portions of contacts 36 and 31 may spread apart to receive the terminal prong 39 of lamp IT. The rearward portions of contacts 38 and 37 are adapted to receive terminal screws 66 and 63.

The socket I4 may comprise a single contact 4| suitably held in an insulating support 42 and having a terminal screw 43. The insulating support 42 may be formed of any suitable material, such for example as Bakelite, and may be received in a metallic cup-shaped shell 44, a spring 45 being disposed as shown for urging the insulator 42 and consequently the terminal 4| outwardly. The two sockets I2 and I4 may be held in a suitable fiuorescent lamp fixture, not shown, and to insert the lamp I6 the single prong 46 is placed into the terminal 4i and sufficient force exerted to move terminal 4I against the force of spring 45 until sufllcient displacement has occurred to permit the reception of single terminal 33 into the socket l2. Thereafter the prong 33 is urged between contacts 29 and SI and the terminal 4I remains in contact with terminal 46 due to the presence of spring 45.

Socket I5 is substantially identical to socket I4 and includes a terminal 41 and a terminal screw 49 held in an insulating support 48. The insulator 48 is held in a metallic cup-shaped member 5I and a spring 52 is disposed to urge the insulator and the terminal outwardly as described in connection with socket 4I. The sockets I3 and I5 may be held in the same fixture as sockets I2 and I4, and to insert lamp I? the same procedure outlined for lamp I6 is followed. That is, the single prong 56 is first inserted into terminal 4'1 followed by insertion of prong 39 between contacts 36 and 31.

The sockets shown and described are a preferred form, but it will be understood that other forms of sockets or switches may be used, it being essential only that appropriate contacts or terminals be provided for completing the circuits to be described.

The source S is connected to contact 3I through a switch 53, a conductor 54 and screw 35. Similarly, the source S is connected to contact 36 through a conductor 65 and screw 66. The contact 29 is connected to lead 25 of the ballast through a conductor 56 and terminal screw 34. Likewise, contact 37 is connected to lead 26 of the ballast through a conductor 51 and terminal screw 63. The terminal 4| is connected to lead 28 of the ballast through a conductor 58 and terminal screw 43, and terminal 41 may be connected to lead 2'! of the ballast through a conductor 59 and terminal screw'49.

The circuit for energizing the primary winding I8 of the transformer may be traced as follows: From source S through conductors 55, contacts 35 and 37, conductor 5'1, lead 25, conductor 6i, winding I8, lead 25, conductor 56, contacts 29 and 3I, conductor 54 and switch 53 to source S. When the terminal prongs of either of lamps I6 and IT are removed from sockets I2 and I3, respectively, a gap exists between the appropriate pairs of contacts 29, 3i and 36, 31 and no excitation can be supplied to winding I8. When, however, both lamps I6 and I1 are disposed with terminal :prongs:.33 and=39 between .the. associ ated pairs of. contacts, the .circuittraced out for winding I8 is complete sinceterminal prongs .33 land .39..are conducting. The'full voltage of the transformer is obtained .across leads 2 5..and .28, and when operating the lamps I6 and Ilare con nected in .aseries. circuit therewith and consequently in series vwith the windings I8 and I9. This series circuit may be traced as follows: From lead 25 through conductor 56, contact: 29,..lamp Ifithrough terminal prongs 33 andilfi, terminal 4!, conductorit, lead 28,.winding I9, conductor 62,-condenser 2|, lead 21, conductor. 59, terminal .47, lamp Il through terminalszEIl and :39, con- Thisshunt circuit may be traced from contact 31 through conductor 51, lead 26, resistor;-22, condenser 23, lead.2l.and.conductor .59 to terminal 41.

Thestarting operationofthe lamp may be understood by visualizing that switch 53 is closed and a source of suitable alternating voltage is thereby connected towinding It. The full voltage of windings I8 and I9 is first applied to lamp l6 through the circuit which may be traced as follows: From winding I8 through lead 25, conductor at, contact 29, lamp It, terminal conductor 58, lead 28, winding I9, conductor 6-2, condenser 2|, condenser 23, resistor .22 and conductor 6| to winding I 8. During the first instant of voltage application no current flows and thus the full voltage of the windings appears across lamp I6. The combined voltage of windings I8 and I9 is sumcient to strike lamp {6 whereupon ionizing current flows therethrough, the ionizing current being not suificient to cause the lamp to reach full brilliance. The current is limited to this ionizing value due largely to the reactance value of condenser 23. The resistor I8 is relatively small in ohmic value compared to the reactance of condenser 23, but is utilized to improve the operation. The ionizing current flowing through the shunt circuit of resistor 22 and condenser 23 develops sufiicient voltage thereacross to strike lamp H, as is well understood in this art. As soon as lamp I'l strikes the voltage therea'cross drops from the high striking value to the much lower operating value whereupon the current flow through the shunt circuit drops to a considerably lower value. After striking in sequence as just described, the lamps operate in series as is understood.

When lamps IIS and Il are properly disposed in their sockets and switch 53 is closed to connect a source of voltage to the apparatus, the high voltage developed by the transformer is applied to the first lamp I5 for starting, the circuit to the primary winding being completed by means of the prong 33 forming a complete circuit between terminals 29 and SI, and the prong 39 forming a complete circuit between terminals as and 3'2. During operation, the voltage existing between prongs 33 and 46 of lamp I6 and prongs 3s and 50 of lamp I"! are much lower, being limited thereto by the ballast. If either of the lamps It and I! should burn out, thereby in effect opening thecircuit between: the respective mterminal prongs of the lamps, the relatively high voltage needed'for striking the lamps vwouldreappear thereacross. If either of the1lanips I6 and I], however, is removed from its socket, whether or not the lamp is burned out, the circuit to the primary winding is opened. by the gaps existing between contacts29, 3| and 36, 31. Consequently,

not appear anywhere else in the circuit. Accordingly, the energizing circuit for the lamps is safe at all times since when a workman removesa lamp, the high voltage in the circuitdisappears and it cannot reappear until the lampis placed into proper position. I

While a particular embodiment of the invention has beenshown, it will be understood, of' course, that the invention is not limited-thereto: since many .modifications may be made, and it is, therefore, contemplated by the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

1..An energizing circuit for two gaseous discharge lamps each lamp having two terminals comprising, transforming means energizable to provide voltageszfor starting and operating said lamps including a primary winding for connection to a voltage source having a certain magnitude and frequency and a secondary winding disposed on a common magnetic core, two pairs of spaced contact means each pair of which is adapted for conductively engaging the terminals of one of such lamps, the first contact means of each pair including two normally spaced-apart contacts capable of receiving one of the terminals of one of such lamps so as to electrically connect it with both the contacts, one of the normally spacedapart contacts of each of said first contact means being connected to a separate end of said primary winding, the other of said normally spaced-apart contacts of each of said first contact means being connectible to a separate terminal of such source, the second contact means of each pair including a lamp terminal engaging contact operatively connected to a separate end of said secondary winding in such manner that when such lamps are disposed in such energizing circuit they are connected in series with each other and said windings are effectively connected in series relationship.

2. An energizing circuit for two gaseous discharge lamps each lamp having two terminals comprising, transforming means energizable to provide voltages for starting and operating said lamps including a primary winding for connection to a voltage source having a certain magnitude and frequency and a secondary winding disposed on a common magnetic core, two pairs of spaced contact means each pair of which is adapted for conductively engaging the terminals of one of such lamps, the first contact means of each pair including two normally spaced-apart contacts capable of contacting one of the terminals of one of such lamps so as to electrically connect it with both the contacts, one of the normally spacedapart contacts of each of said first contact means being connected to a separate end of said primary winding, the other of said normally spacedapart contacts of each of said first contact means being connectible to a separate terminal of such source, the second contact means of each pair including a lamp terminal engaging contact operatively connected to a separate end of said secondary winding in such manner that when such lamps are disposed in such energizing circuit they are connected in series with each other and said windings are efiectively connected in series relationship.

3. An energizing circuit for two gaseous discharge lamps each lamp having two terminals according to claim 1, characterized in that the primary and the secondary windings are effectively connected in autotransformer relationship in additive polarity.

4. An energizing circuit for two gaseous discharge lamps each lamp having two terminals according to claim 1, characterized in that the core and the primary and secondary windings are so constructed and arranged as to produce a high magnetic leakage reactance efiect, a shunt circuit comprising a resistor and a condenser is connected in circuit between the windings and a condenser is connected in circuit with the secondary Winding.

5. An energizing circuit for a plurality of gaseouse discharge lamps each lamp having two terminals comprising, transforming means energizable to provide voltages for starting and operating said lamps including a primary Winding for connection to a voltage source having a certain magnitude and frequency and a secondary winding disposed on a common magnetic core, two pairs of spaced contact means each pair of which is adapted for conductively engaging the terminals of one of such lamps, the first contact means of each pair including two normally spaced-apart contacts capable of receiving one of the terminals of one of such lamps so as to electrically connect it With both the contacts, one of the normally spaced-apart contacts of each of said first contact means being connected to a separate end of said primary winding, the other of said normally spaced-apart contacts of each of said first contact means being connectible to a separate terminal of such source, the second contact means of each pair including a lamp terminal engaging contact operatively connected to a separate end of said second winding in such manner that when such plurality of lamps are disposed in such energizing circuit they are connected in series with each other and said windings are effectively connected in series relationship.

CARL A. PETERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,689,485 Hendry Oct. 30, 1928 2,295,757 Russell Sept. 15, 1942 2,427,225 Mueller Sept. 9, 1947 2,464,971 Flood Mar. 22, 1949 

